If I remember correctly they come in various sizes. Basically it has course reversed threads that expand quickly so that it digs into the stuck bolt or in this case plug. once it digs in and sticks it will hopefully loosen the plug. They are sold in REAL auto parts stores here where I live, but not at places like autozone etc. Spend some time on the phone with you local auto parts stores, they should know of a solution. Best of luck to ya!